Liposoluble bioactive compounds are often included in foods in emulsified lipid carriers. In the present study, the impact of the physical state of the lipid carrier and the interfacial composition of oil-in-water emulsions on the stability of β-carotene was studied. Emulsions with hydrogenated palm kernel oil (HPKO) concentration of 10% (w/w) dispersing 0.05% (w/w) β-carotene, and a water phase at pH 7 containing 30% (w/w) sucrose, were stabilized by 1%, 1.5%, 2%, and 3% (w/w) whey protein isolate (WPI). Crystallization and melting behavior of emulsified and bulk HPKO were studied by differential scanning calorimetry. The hysteresis of emulsified HPKO crystallization (onset approximately 10 °C; endset approximately 6 °C) and melting (onset approximately 17 °C; endset approximately 45 °C) allowed us to operate at 15 °C on systems with identical compositions but different physical states of the same lipid phase. Surface protein coverage of emulsions was calculated and size of the dispersed particles was characterized by dynamic light scattering. β-Carotene contents of the emulsions during storage at 15 °C was analyzed spectrophotometerically. Results highlighted an impact of the phase of the lipid carrier and of the concentration of WPI on β-carotene degradation. β-Carotene loss showed zero-order kinetics. A liquid dispersed phase resulted in a low degradation rate but a high concentration of protein on a solid lipid carrier was likewise effective for β-carotene protection. Practical Application: The inclusion of lipophilic bioactive compounds, such as carotenoids, is a current trend in the production of functional foods aiming to enhance health and well-being. However, the use of functional ingredients in food products is complicated because of the sensitivity of the active molecules to physical and chemical factors to which they are exposed during processing, storage, and consumption. The present work gives indications of the influence of the lipid carrier physical state and surface structure on ß-carotene stability in formulated oil-in-water liquid food models, suggesting possible strategies for an enhanced stabilization of lipophilic labile compounds.
© 2011 Institute of Food Technologists®